Explanation:

The Survey of India, headquartered at Dehra Dun, has 18 Geo Spatial divisions ranging from the prediction of tides to aerial survey. It has 23 Geo-spatial Data Centers spread across India, each catering to the respective administrative area.Surveyors are the back bone of Survey of India. Appointments to Group 'A' Civil Stream posts in the Junior Time Scale (Dy Supdtg Surveyor) in Survey of India are made on the basis of competitive Indian Engineering Services examination conducted by the Union Public Service Commission and also through permanent secondment of Army Officers Defence Stream by the Union Public Service Commission.